Auto tokenizer registration (#23965)

add check loop over extra content

src/transformers/models/auto/configuration_auto.py

@@ -645,6 +645,10 @@ def config_class_to_model_type(config):
     for key, cls in CONFIG_MAPPING_NAMES.items():
         if cls == config:
             return key
+    # if key not found check in extra content
+    for key, cls in CONFIG_MAPPING._extra_content.items():
+        if cls.__name__ == config:
+            return key
     return None